sntp.c

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/**
 * @file
 * SNTP client module
 *
 * This is simple "SNTP" client for the lwIP raw API.
 * It is a minimal implementation of SNTPv4 as specified in RFC 4330.
 * 
 * For a list of some public NTP servers, see this link :
 * http://support.ntp.org/bin/view/Servers/NTPPoolServers
 *
 * @todo:
 * - set/change servers at runtime
 * - complete SNTP_CHECK_RESPONSE checks 3 and 4
 * - support broadcast/multicast mode?
 */

/*
 * Redistribution and use in source and binary forms, with or without modification, 
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission. 
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED 
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT 
 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT 
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING 
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY 
 * OF SUCH DAMAGE.
 *
 * This file is part of the lwIP TCP/IP stack.
 * 
 * Author: Simon Goldschmidt (lwIP raw API part)
 */

#include "lwip/sntp.h"
#include "osapi.h"
#include "os_type.h"
#include "lwip/opt.h"
#include "lwip/timers.h"
#include "lwip/udp.h"
#include "lwip/dns.h"
#include "lwip/ip_addr.h"
#include "lwip/pbuf.h"

//#include <string.h>
#if LWIP_UDP

/**
 * SNTP_DEBUG: Enable debugging for SNTP.
 */
#ifndef SNTP_DEBUG
#define SNTP_DEBUG                  LWIP_DBG_ON
#endif

/** SNTP server port */
#ifndef SNTP_PORT
#define SNTP_PORT                   123
#endif

/** Set this to 1 to allow config of SNTP server(s) by DNS name */
#ifndef SNTP_SERVER_DNS
#define SNTP_SERVER_DNS             0
#endif

/** Handle support for more than one server via NTP_MAX_SERVERS,
 * but catch legacy style of setting SNTP_SUPPORT_MULTIPLE_SERVERS, probably outside of this file
 */
#ifndef SNTP_SUPPORT_MULTIPLE_SERVERS
#if SNTP_MAX_SERVERS > 1
#define SNTP_SUPPORT_MULTIPLE_SERVERS 1
#else /* NTP_MAX_SERVERS > 1 */
#define SNTP_SUPPORT_MULTIPLE_SERVERS 0
#endif /* NTP_MAX_SERVERS > 1 */
#else /* SNTP_SUPPORT_MULTIPLE_SERVERS */
/* The developer has defined SNTP_SUPPORT_MULTIPLE_SERVERS, probably from old code */
#if SNTP_MAX_SERVERS <= 1
#error "SNTP_MAX_SERVERS needs to be defined to the max amount of servers if SNTP_SUPPORT_MULTIPLE_SERVERS is defined"
#endif /* SNTP_MAX_SERVERS <= 1 */
#endif /* SNTP_SUPPORT_MULTIPLE_SERVERS */


/** Sanity check:
 * Define this to
 * - 0 to turn off sanity checks (default; smaller code)
 * - >= 1 to check address and port of the response packet to ensure the
 *        response comes from the server we sent the request to.
 * - >= 2 to check returned Originate Timestamp against Transmit Timestamp
 *        sent to the server (to ensure response to older request).
 * - >= 3 @todo: discard reply if any of the LI, Stratum, or Transmit Timestamp
 *        fields is 0 or the Mode field is not 4 (unicast) or 5 (broadcast).
 * - >= 4 @todo: to check that the Root Delay and Root Dispersion fields are each
 *        greater than or equal to 0 and less than infinity, where infinity is
 *        currently a cozy number like one second. This check avoids using a
 *        server whose synchronization source has expired for a very long time.
 */
#ifndef SNTP_CHECK_RESPONSE
#define SNTP_CHECK_RESPONSE         0
#endif

/** According to the RFC, this shall be a random delay
 * between 1 and 5 minutes (in milliseconds) to prevent load peaks.
 * This can be defined to a random generation function,
 * which must return the delay in milliseconds as u32_t.
 * Turned off by default.
 */
#ifndef SNTP_STARTUP_DELAY
#define SNTP_STARTUP_DELAY          0
#endif

/** If you want the startup delay to be a function, define this
 * to a function (including the brackets) and define SNTP_STARTUP_DELAY to 1.
 */
#ifndef SNTP_STARTUP_DELAY_FUNC
#define SNTP_STARTUP_DELAY_FUNC     SNTP_STARTUP_DELAY
#endif

/** SNTP receive timeout - in milliseconds
 * Also used as retry timeout - this shouldn't be too low.
 * Default is 3 seconds.
 */
#ifndef SNTP_RECV_TIMEOUT
#define SNTP_RECV_TIMEOUT           3000
#endif

/** SNTP update delay - in milliseconds
 * Default is 1 hour.
 */
#ifndef SNTP_UPDATE_DELAY
#define SNTP_UPDATE_DELAY           3600000
#endif
#if (SNTP_UPDATE_DELAY < 15000) && !SNTP_SUPPRESS_DELAY_CHECK
#error "SNTPv4 RFC 4330 enforces a minimum update time of 15 seconds!"
#endif

/** SNTP macro to change system time and/or the update the RTC clock */
#ifndef SNTP_SET_SYSTEM_TIME
#define SNTP_SET_SYSTEM_TIME(sec) ((void)sec)
#endif

/** SNTP macro to change system time including microseconds */
#ifdef SNTP_SET_SYSTEM_TIME_US
#define SNTP_CALC_TIME_US           1
#define SNTP_RECEIVE_TIME_SIZE      2
#else
#define SNTP_SET_SYSTEM_TIME_US(sec, us)
#define SNTP_CALC_TIME_US           0
#define SNTP_RECEIVE_TIME_SIZE      1
#endif

/** SNTP macro to get system time, used with SNTP_CHECK_RESPONSE >= 2
 * to send in request and compare in response.
 */
#ifndef SNTP_GET_SYSTEM_TIME
#define SNTP_GET_SYSTEM_TIME(sec, us)     do { (sec) = 0; (us) = 0; } while(0)
#endif

/** Default retry timeout (in milliseconds) if the response
 * received is invalid.
 * This is doubled with each retry until SNTP_RETRY_TIMEOUT_MAX is reached.
 */
#ifndef SNTP_RETRY_TIMEOUT
#define SNTP_RETRY_TIMEOUT          SNTP_RECV_TIMEOUT
#endif

/** Maximum retry timeout (in milliseconds). */
#ifndef SNTP_RETRY_TIMEOUT_MAX
#define SNTP_RETRY_TIMEOUT_MAX      (SNTP_RETRY_TIMEOUT * 10)
#endif

/** Increase retry timeout with every retry sent
 * Default is on to conform to RFC.
 */
#ifndef SNTP_RETRY_TIMEOUT_EXP
#define SNTP_RETRY_TIMEOUT_EXP      1
#endif

/* the various debug levels for this file */
#define SNTP_DEBUG_TRACE        (SNTP_DEBUG | LWIP_DBG_TRACE)
#define SNTP_DEBUG_STATE        (SNTP_DEBUG | LWIP_DBG_STATE)
#define SNTP_DEBUG_WARN         (SNTP_DEBUG | LWIP_DBG_LEVEL_WARNING)
#define SNTP_DEBUG_WARN_STATE   (SNTP_DEBUG | LWIP_DBG_LEVEL_WARNING | LWIP_DBG_STATE)
#define SNTP_DEBUG_SERIOUS      (SNTP_DEBUG | LWIP_DBG_LEVEL_SERIOUS)

#define SNTP_ERR_KOD                1

/* SNTP protocol defines */
#define SNTP_MSG_LEN                48

#define SNTP_OFFSET_LI_VN_MODE      0
#define SNTP_LI_MASK                0xC0
#define SNTP_LI_NO_WARNING          0x00
#define SNTP_LI_LAST_MINUTE_61_SEC  0x01
#define SNTP_LI_LAST_MINUTE_59_SEC  0x02
#define SNTP_LI_ALARM_CONDITION     0x03 /* (clock not synchronized) */

#define SNTP_VERSION_MASK           0x38
#define SNTP_VERSION                (4/* NTP Version 4*/<<3) 

#define SNTP_MODE_MASK              0x07
#define SNTP_MODE_CLIENT            0x03
#define SNTP_MODE_SERVER            0x04
#define SNTP_MODE_BROADCAST         0x05

#define SNTP_OFFSET_STRATUM         1
#define SNTP_STRATUM_KOD            0x00

#define SNTP_OFFSET_ORIGINATE_TIME  24
#define SNTP_OFFSET_RECEIVE_TIME    32
#define SNTP_OFFSET_TRANSMIT_TIME   40

/* number of seconds between 1900 and 1970 */
#define DIFF_SEC_1900_1970         (2208988800UL)

/**
 * SNTP packet format (without optional fields)
 * Timestamps are coded as 64 bits:
 * - 32 bits seconds since Jan 01, 1970, 00:00
 * - 32 bits seconds fraction (0-padded)
 * For future use, if the MSB in the seconds part is set, seconds are based
 * on Feb 07, 2036, 06:28:16.
 */
#ifdef PACK_STRUCT_USE_INCLUDES
#  include "arch/bpstruct.h"
#endif
PACK_STRUCT_BEGIN
#define PACK_STRUCT_FLD_8 PACK_STRUCT_FIELD
struct sntp_msg {
  PACK_STRUCT_FLD_8(u8_t           li_vn_mode);
  PACK_STRUCT_FLD_8(u8_t           stratum);
  PACK_STRUCT_FLD_8(u8_t           poll);
  PACK_STRUCT_FLD_8(u8_t           precision);
  PACK_STRUCT_FIELD(u32_t          root_delay);
  PACK_STRUCT_FIELD(u32_t          root_dispersion);
  PACK_STRUCT_FIELD(u32_t          reference_identifier);
  PACK_STRUCT_FIELD(u32_t          reference_timestamp[2]);
  PACK_STRUCT_FIELD(u32_t          originate_timestamp[2]);
  PACK_STRUCT_FIELD(u32_t          receive_timestamp[2]);
  PACK_STRUCT_FIELD(u32_t          transmit_timestamp[2]);
} PACK_STRUCT_STRUCT;
PACK_STRUCT_END
#ifdef PACK_STRUCT_USE_INCLUDES
#  include "arch/epstruct.h"
#endif

/* function prototypes */
static void sntp_request(void *arg);

/** The UDP pcb used by the SNTP client */
static struct udp_pcb* sntp_pcb;

sint8 time_zone = 8;
/** Names/Addresses of servers */
struct sntp_server {
#if SNTP_SERVER_DNS
  char* name;
#endif /* SNTP_SERVER_DNS */
  ip_addr_t addr;
};
static struct sntp_server sntp_servers[SNTP_MAX_SERVERS];

static u8_t sntp_set_servers_from_dhcp;
#if SNTP_SUPPORT_MULTIPLE_SERVERS
/** The currently used server (initialized to 0) */
static u8_t sntp_current_server;
#else /* SNTP_SUPPORT_MULTIPLE_SERVERS */
#define sntp_current_server 0
#endif /* SNTP_SUPPORT_MULTIPLE_SERVERS */

#if SNTP_RETRY_TIMEOUT_EXP
#define SNTP_RESET_RETRY_TIMEOUT() sntp_retry_timeout = SNTP_RETRY_TIMEOUT
/** Retry time, initialized with SNTP_RETRY_TIMEOUT and doubled with each retry. */
static u32_t sntp_retry_timeout;
#else /* SNTP_RETRY_TIMEOUT_EXP */
#define SNTP_RESET_RETRY_TIMEOUT()
#define sntp_retry_timeout SNTP_RETRY_TIMEOUT
#endif /* SNTP_RETRY_TIMEOUT_EXP */

#if SNTP_CHECK_RESPONSE >= 1
/** Saves the last server address to compare with response */
static ip_addr_t sntp_last_server_address;
#endif /* SNTP_CHECK_RESPONSE >= 1 */

#if SNTP_CHECK_RESPONSE >= 2
/** Saves the last timestamp sent (which is sent back by the server)
 * to compare against in response */
static u32_t sntp_last_timestamp_sent[2];
#endif /* SNTP_CHECK_RESPONSE >= 2 */
typedef long     time_t;
//uint32 current_stamp_1 = 0;
//uint32 current_stamp_2 = 0;
uint32 realtime_stamp = 0;
LOCAL os_timer_t sntp_timer;
/*****************************************/
#define SECSPERMIN  60L
#define MINSPERHOUR 60L
#define HOURSPERDAY 24L
#define SECSPERHOUR (SECSPERMIN * MINSPERHOUR)
#define SECSPERDAY  (SECSPERHOUR * HOURSPERDAY)
#define DAYSPERWEEK 7
#define MONSPERYEAR 12

#define YEAR_BASE   1900
#define EPOCH_YEAR      1970
#define EPOCH_WDAY      4
#define EPOCH_YEARS_SINCE_LEAP 2
#define EPOCH_YEARS_SINCE_CENTURY 70
#define EPOCH_YEARS_SINCE_LEAP_CENTURY 370

#define isleap(y) ((((y) % 4) == 0 && ((y) % 100) != 0) || ((y) % 400) == 0)

int __tznorth;
int __tzyear;
char reult[100];
static const int mon_lengths[2][12] = {
  {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
  {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
} ;

static const int year_lengths[2] = {
  365,
  366
} ;
struct tm
{
  int   tm_sec;
  int   tm_min;
  int   tm_hour;
  int   tm_mday;
  int   tm_mon;
  int   tm_year;
  int   tm_wday;
  int   tm_yday;
  int   tm_isdst;
};

struct tm res_buf;
typedef struct __tzrule_struct
{
  char ch;
  int m;
  int n;
  int d;
  int s;
  time_t change;
  int offset;
} __tzrule_type;

__tzrule_type sntp__tzrule[2];
struct tm * ICACHE_FLASH_ATTR
sntp_mktm_r(const time_t * tim_p ,struct tm *res ,int is_gmtime)
{
  long days, rem;
  time_t lcltime;
  int i;
  int y;
  int yleap;
  const int *ip;

  /* base decision about std/dst time on current time */
  lcltime = *tim_p;

  days = ((long)lcltime) / SECSPERDAY;
  rem = ((long)lcltime) % SECSPERDAY;
  while (rem < 0)
    {
      rem += SECSPERDAY;
      --days;
    }
  while (rem >= SECSPERDAY)
    {
      rem -= SECSPERDAY;
      ++days;
    }

  /* compute hour, min, and sec */
  res->tm_hour = (int) (rem / SECSPERHOUR);
  rem %= SECSPERHOUR;
  res->tm_min = (int) (rem / SECSPERMIN);
  res->tm_sec = (int) (rem % SECSPERMIN);

  /* compute day of week */
  if ((res->tm_wday = ((EPOCH_WDAY + days) % DAYSPERWEEK)) < 0)
    res->tm_wday += DAYSPERWEEK;

  /* compute year & day of year */
  y = EPOCH_YEAR;
  if (days >= 0)
    {
      for (;;)
    {
      yleap = isleap(y);
      if (days < year_lengths[yleap])
        break;
      y++;
      days -= year_lengths[yleap];
    }
    }
  else
    {
      do
    {
      --y;
      yleap = isleap(y);
      days += year_lengths[yleap];
    } while (days < 0);
    }

  res->tm_year = y - YEAR_BASE;
  res->tm_yday = days;
  ip = mon_lengths[yleap];
  for (res->tm_mon = 0; days >= ip[res->tm_mon]; ++res->tm_mon)
    days -= ip[res->tm_mon];
  res->tm_mday = days + 1;

  if (!is_gmtime)
    {
      int offset;
      int hours, mins, secs;

//      TZ_LOCK;
//      if (_daylight)
//  {
//    if (y == __tzyear || __tzcalc_limits (y))
//      res->tm_isdst = (__tznorth
//               ? (*tim_p >= __tzrule[0].change && *tim_p < __tzrule[1].change)
//               : (*tim_p >= __tzrule[0].change || *tim_p < __tzrule[1].change));
//    else
//      res->tm_isdst = -1;
//  }
//      else
    res->tm_isdst = 0;

      offset = (res->tm_isdst == 1 ? sntp__tzrule[1].offset : sntp__tzrule[0].offset);

      hours = offset / SECSPERHOUR;
      offset = offset % SECSPERHOUR;

      mins = offset / SECSPERMIN;
      secs = offset % SECSPERMIN;

      res->tm_sec -= secs;
      res->tm_min -= mins;
      res->tm_hour -= hours;

      if (res->tm_sec >= SECSPERMIN)
    {
      res->tm_min += 1;
      res->tm_sec -= SECSPERMIN;
    }
      else if (res->tm_sec < 0)
    {
      res->tm_min -= 1;
      res->tm_sec += SECSPERMIN;
    }
      if (res->tm_min >= MINSPERHOUR)
    {
      res->tm_hour += 1;
      res->tm_min -= MINSPERHOUR;
    }
      else if (res->tm_min < 0)
    {
      res->tm_hour -= 1;
      res->tm_min += MINSPERHOUR;
    }
      if (res->tm_hour >= HOURSPERDAY)
    {
      ++res->tm_yday;
      ++res->tm_wday;
      if (res->tm_wday > 6)
        res->tm_wday = 0;
      ++res->tm_mday;
      res->tm_hour -= HOURSPERDAY;
      if (res->tm_mday > ip[res->tm_mon])
        {
          res->tm_mday -= ip[res->tm_mon];
          res->tm_mon += 1;
          if (res->tm_mon == 12)
        {
          res->tm_mon = 0;
          res->tm_year += 1;
          res->tm_yday = 0;
        }
        }
    }
       else if (res->tm_hour < 0)
    {
      res->tm_yday -= 1;
      res->tm_wday -= 1;
      if (res->tm_wday < 0)
        res->tm_wday = 6;
      res->tm_mday -= 1;
      res->tm_hour += 24;
      if (res->tm_mday == 0)
        {
          res->tm_mon -= 1;
          if (res->tm_mon < 0)
        {
          res->tm_mon = 11;
          res->tm_year -= 1;
          res->tm_yday = 365 + isleap(res->tm_year);
        }
          res->tm_mday = ip[res->tm_mon];
        }
    }
//      TZ_UNLOCK;
    }
  else
    res->tm_isdst = 0;
//  os_printf("res %d %d %d %d %d\n",res->tm_year,res->tm_mon,res->tm_mday,res->tm_yday,res->tm_hour);
  return (res);
}
struct tm * ICACHE_FLASH_ATTR
sntp_localtime_r(const time_t * tim_p ,
        struct tm *res)
{
  return sntp_mktm_r (tim_p, res, 0);
}

struct tm * ICACHE_FLASH_ATTR
sntp_localtime(const time_t * tim_p)
{
  return sntp_localtime_r (tim_p, &res_buf);
}


int ICACHE_FLASH_ATTR
sntp__tzcalc_limits(int year)
{
  int days, year_days, years;
  int i, j;

  if (year < EPOCH_YEAR)
    return 0;

  __tzyear = year;

  years = (year - EPOCH_YEAR);

  year_days = years * 365 +
    (years - 1 + EPOCH_YEARS_SINCE_LEAP) / 4 - (years - 1 + EPOCH_YEARS_SINCE_CENTURY) / 100 +
    (years - 1 + EPOCH_YEARS_SINCE_LEAP_CENTURY) / 400;

  for (i = 0; i < 2; ++i)
    {
      if (sntp__tzrule[i].ch == 'J')
    days = year_days + sntp__tzrule[i].d + (isleap(year) && sntp__tzrule[i].d >= 60);
      else if (sntp__tzrule[i].ch == 'D')
    days = year_days + sntp__tzrule[i].d;
      else
    {
      int yleap = isleap(year);
      int m_day, m_wday, wday_diff;
      const int *ip = mon_lengths[yleap];

      days = year_days;

      for (j = 1; j < sntp__tzrule[i].m; ++j)
        days += ip[j-1];

      m_wday = (EPOCH_WDAY + days) % DAYSPERWEEK;

      wday_diff = sntp__tzrule[i].d - m_wday;
      if (wday_diff < 0)
        wday_diff += DAYSPERWEEK;
      m_day = (sntp__tzrule[i].n - 1) * DAYSPERWEEK + wday_diff;

      while (m_day >= ip[j-1])
        m_day -= DAYSPERWEEK;

      days += m_day;
    }

      /* store the change-over time in GMT form by adding offset */
      sntp__tzrule[i].change = days * SECSPERDAY + sntp__tzrule[i].s + sntp__tzrule[i].offset;
    }

  __tznorth = (sntp__tzrule[0].change < sntp__tzrule[1].change);

  return 1;
}

char * ICACHE_FLASH_ATTR
sntp_asctime_r(struct tm *tim_p ,char *result)
{
  static const char day_name[7][4] = {
    "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
  };
  static const char mon_name[12][4] = {
    "Jan", "Feb", "Mar", "Apr", "May", "Jun",
    "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
  };
  os_sprintf (result, "%s %s %02d %02d:%02d:%02d %02d\n",
       day_name[tim_p->tm_wday],
       mon_name[tim_p->tm_mon],
       tim_p->tm_mday, tim_p->tm_hour, tim_p->tm_min,
       tim_p->tm_sec, 1900 + tim_p->tm_year);
  return result;
}
char *ICACHE_FLASH_ATTR
sntp_asctime(struct tm *tim_p)
{

    return sntp_asctime_r (tim_p, reult);
}

uint32 sntp_get_current_timestamp()
{
    if(realtime_stamp == 0){
        os_printf("please start sntp first !\n");
        return 0;
    } else {
        return realtime_stamp;
    }
}

char* sntp_get_real_time(time_t t)
{
    return sntp_asctime(sntp_localtime (&t));
}
/**
 * SNTP get time_zone default GMT + 8
 */
sint8 ICACHE_FLASH_ATTR
sntp_get_timezone(void)
{
    return time_zone;
}
/**
 * SNTP set time_zone default GMT + 8
 */

bool ICACHE_FLASH_ATTR
sntp_set_timezone(sint8 timezone)
{
    if(timezone >= -11 || timezone <= 13) {
        time_zone = timezone;
        return true;
    } else {
        return false;
    }

}
void ICACHE_FLASH_ATTR
sntp_time_inc(void)
{
    realtime_stamp++;
}
/**
 * SNTP processing of received timestamp
 */
static void ICACHE_FLASH_ATTR
sntp_process(u32_t *receive_timestamp)
{
  /* convert SNTP time (1900-based) to unix GMT time (1970-based)
   * @todo: if MSB is 1, SNTP time is 2036-based!
   */
  time_t t = (ntohl(receive_timestamp[0]) - DIFF_SEC_1900_1970);

#if SNTP_CALC_TIME_US
  u32_t us = ntohl(receive_timestamp[1]) / 4295;
  SNTP_SET_SYSTEM_TIME_US(t, us);
  /* display local time from GMT time */
  LWIP_DEBUGF(SNTP_DEBUG_TRACE, ("sntp_process: %s, %"U32_F" us", ctime(&t), us));

#else /* SNTP_CALC_TIME_US */

  /* change system time and/or the update the RTC clock */
  SNTP_SET_SYSTEM_TIME(t);
  /* display local time from GMT time */
  t += time_zone * 60 * 60;// format GMT + time_zone TIME ZONE
  realtime_stamp = t;
  os_timer_disarm(&sntp_timer);
  os_timer_setfn(&sntp_timer, (os_timer_func_t *)sntp_time_inc, NULL);
  os_timer_arm(&sntp_timer, 1000, 1);
  os_printf("%s\n",sntp_asctime(sntp_localtime (&t)));
//  os_printf("%s\n",ctime(&t));
//  LWIP_DEBUGF(SNTP_DEBUG_TRACE, ("sntp_process: %s", ctime(&t)));
#endif /* SNTP_CALC_TIME_US */
}

/**
 * Initialize request struct to be sent to server.
 */
static void ICACHE_FLASH_ATTR
sntp_initialize_request(struct sntp_msg *req)
{
  os_memset(req, 0, SNTP_MSG_LEN);
  req->li_vn_mode = SNTP_LI_NO_WARNING | SNTP_VERSION | SNTP_MODE_CLIENT;

#if SNTP_CHECK_RESPONSE >= 2
  {
    u32_t sntp_time_sec, sntp_time_us;
    /* fill in transmit timestamp and save it in 'sntp_last_timestamp_sent' */
    SNTP_GET_SYSTEM_TIME(sntp_time_sec, sntp_time_us);
    sntp_last_timestamp_sent[0] = htonl(sntp_time_sec + DIFF_SEC_1900_1970);
    req->transmit_timestamp[0] = sntp_last_timestamp_sent[0];
    /* we send/save us instead of fraction to be faster... */
    sntp_last_timestamp_sent[1] = htonl(sntp_time_us);
    req->transmit_timestamp[1] = sntp_last_timestamp_sent[1];
  }
#endif /* SNTP_CHECK_RESPONSE >= 2 */
}

/**
 * Retry: send a new request (and increase retry timeout).
 *
 * @param arg is unused (only necessary to conform to sys_timeout)
 */
static void ICACHE_FLASH_ATTR
sntp_retry(void* arg)
{
  LWIP_UNUSED_ARG(arg);

  LWIP_DEBUGF(SNTP_DEBUG_STATE, ("sntp_retry: Next request will be sent in %"U32_F" ms\n",
    sntp_retry_timeout));

  /* set up a timer to send a retry and increase the retry delay */
  sys_timeout(sntp_retry_timeout, sntp_request, NULL);

#if SNTP_RETRY_TIMEOUT_EXP
  {
    u32_t new_retry_timeout;
    /* increase the timeout for next retry */
    new_retry_timeout = sntp_retry_timeout << 1;
    /* limit to maximum timeout and prevent overflow */
    if ((new_retry_timeout <= SNTP_RETRY_TIMEOUT_MAX) &&
        (new_retry_timeout > sntp_retry_timeout)) {
      sntp_retry_timeout = new_retry_timeout;
    }
  }
#endif /* SNTP_RETRY_TIMEOUT_EXP */
}

#if SNTP_SUPPORT_MULTIPLE_SERVERS
/**
 * If Kiss-of-Death is received (or another packet parsing error),
 * try the next server or retry the current server and increase the retry
 * timeout if only one server is available.
 * (implicitly, SNTP_MAX_SERVERS > 1)
 *
 * @param arg is unused (only necessary to conform to sys_timeout)
 */
static void
sntp_try_next_server(void* arg)
{
  u8_t old_server, i;
  LWIP_UNUSED_ARG(arg);

  old_server = sntp_current_server;
  for (i = 0; i < SNTP_MAX_SERVERS - 1; i++) {
    sntp_current_server++;
    if (sntp_current_server >= SNTP_MAX_SERVERS) {
      sntp_current_server = 0;
    }
    if (!ip_addr_isany(&sntp_servers[sntp_current_server].addr)
#if SNTP_SERVER_DNS
        || (sntp_servers[sntp_current_server].name != NULL)
#endif
        ) {
      LWIP_DEBUGF(SNTP_DEBUG_STATE, ("sntp_try_next_server: Sending request to server %"U16_F"\n",
        (u16_t)sntp_current_server));
      /* new server: reset retry timeout */
      SNTP_RESET_RETRY_TIMEOUT();
      /* instantly send a request to the next server */
      sntp_request(NULL);
      return;
    }
  }
  /* no other valid server found */
  sntp_current_server = old_server;
  sntp_retry(NULL);
}
#else /* SNTP_SUPPORT_MULTIPLE_SERVERS */
/* Always retry on error if only one server is supported */
#define sntp_try_next_server    sntp_retry
#endif /* SNTP_SUPPORT_MULTIPLE_SERVERS */

/** UDP recv callback for the sntp pcb */
static void ICACHE_FLASH_ATTR
sntp_recv(void *arg, struct udp_pcb* pcb, struct pbuf *p, ip_addr_t *addr, u16_t port)
{
  u8_t mode;
  u8_t stratum;
  u32_t receive_timestamp[SNTP_RECEIVE_TIME_SIZE];
  err_t err;
//os_printf("sntp_recv\n");
  LWIP_UNUSED_ARG(arg);
  LWIP_UNUSED_ARG(pcb);

  /* packet received: stop retry timeout  */
  sys_untimeout(sntp_try_next_server, NULL);
  sys_untimeout(sntp_request, NULL);

  err = ERR_ARG;
#if SNTP_CHECK_RESPONSE >= 1
  /* check server address and port */
  if (ip_addr_cmp(addr, &sntp_last_server_address) &&
    (port == SNTP_PORT))
#else /* SNTP_CHECK_RESPONSE >= 1 */
  LWIP_UNUSED_ARG(addr);
  LWIP_UNUSED_ARG(port);
#endif /* SNTP_CHECK_RESPONSE >= 1 */
  {
    /* process the response */
    if (p->tot_len == SNTP_MSG_LEN) {
      pbuf_copy_partial(p, &mode, 1, SNTP_OFFSET_LI_VN_MODE);
      mode &= SNTP_MODE_MASK;
      /* if this is a SNTP response... */
      if ((mode == SNTP_MODE_SERVER) ||
          (mode == SNTP_MODE_BROADCAST)) {
        pbuf_copy_partial(p, &stratum, 1, SNTP_OFFSET_STRATUM);
        if (stratum == SNTP_STRATUM_KOD) {
          /* Kiss-of-death packet. Use another server or increase UPDATE_DELAY. */
          err = SNTP_ERR_KOD;
          LWIP_DEBUGF(SNTP_DEBUG_STATE, ("sntp_recv: Received Kiss-of-Death\n"));
        } else {
#if SNTP_CHECK_RESPONSE >= 2
          /* check originate_timetamp against sntp_last_timestamp_sent */
          u32_t originate_timestamp[2];
          pbuf_copy_partial(p, &originate_timestamp, 8, SNTP_OFFSET_ORIGINATE_TIME);
          if ((originate_timestamp[0] != sntp_last_timestamp_sent[0]) ||
              (originate_timestamp[1] != sntp_last_timestamp_sent[1]))
          {
            LWIP_DEBUGF(SNTP_DEBUG_WARN, ("sntp_recv: Invalid originate timestamp in response\n"));
          } else
#endif /* SNTP_CHECK_RESPONSE >= 2 */
          /* @todo: add code for SNTP_CHECK_RESPONSE >= 3 and >= 4 here */
          {
            /* correct answer */
            err = ERR_OK;
            pbuf_copy_partial(p, &receive_timestamp, SNTP_RECEIVE_TIME_SIZE * 4, SNTP_OFFSET_RECEIVE_TIME);
          }
        }
      } else {
        LWIP_DEBUGF(SNTP_DEBUG_WARN, ("sntp_recv: Invalid mode in response: %"U16_F"\n", (u16_t)mode));
      }
    } else {
      LWIP_DEBUGF(SNTP_DEBUG_WARN, ("sntp_recv: Invalid packet length: %"U16_F"\n", p->tot_len));
    }
  }
  pbuf_free(p);
  if (err == ERR_OK) {
    /* Correct response, reset retry timeout */
    SNTP_RESET_RETRY_TIMEOUT();

    sntp_process(receive_timestamp);

    /* Set up timeout for next request */
    sys_timeout((u32_t)SNTP_UPDATE_DELAY, sntp_request, NULL);
    LWIP_DEBUGF(SNTP_DEBUG_STATE, ("sntp_recv: Scheduled next time request: %"U32_F" ms\n",
      (u32_t)SNTP_UPDATE_DELAY));
  } else if (err == SNTP_ERR_KOD) {
    /* Kiss-of-death packet. Use another server or increase UPDATE_DELAY. */
    sntp_try_next_server(NULL);
  } else {
    /* another error, try the same server again */
    sntp_retry(NULL);
  }
}

/** Actually send an sntp request to a server.
 *
 * @param server_addr resolved IP address of the SNTP server
 */
static void ICACHE_FLASH_ATTR
sntp_send_request(ip_addr_t *server_addr)
{
  struct pbuf* p;
//  os_printf("sntp_send_request\n");
  p = pbuf_alloc(PBUF_TRANSPORT, SNTP_MSG_LEN, PBUF_RAM);
  if (p != NULL) {
    struct sntp_msg *sntpmsg = (struct sntp_msg *)p->payload;
    LWIP_DEBUGF(SNTP_DEBUG_STATE, ("sntp_send_request: Sending request to server\n"));
    /* initialize request message */
    sntp_initialize_request(sntpmsg);
    /* send request */
    udp_sendto(sntp_pcb, p, server_addr, SNTP_PORT);
    /* free the pbuf after sending it */
    pbuf_free(p);
    /* set up receive timeout: try next server or retry on timeout */
    sys_timeout((u32_t)SNTP_RECV_TIMEOUT, sntp_try_next_server, NULL);
#if SNTP_CHECK_RESPONSE >= 1
    /* save server address to verify it in sntp_recv */ 
    ip_addr_set(&sntp_last_server_address, server_addr);
#endif /* SNTP_CHECK_RESPONSE >= 1 */
  } else {
    LWIP_DEBUGF(SNTP_DEBUG_SERIOUS, ("sntp_send_request: Out of memory, trying again in %"U32_F" ms\n",
      (u32_t)SNTP_RETRY_TIMEOUT));
    /* out of memory: set up a timer to send a retry */
    sys_timeout((u32_t)SNTP_RETRY_TIMEOUT, sntp_request, NULL);
  }
}

#if SNTP_SERVER_DNS
/**
 * DNS found callback when using DNS names as server address.
 */
static void
sntp_dns_found(const char* hostname, ip_addr_t *ipaddr, void *arg)
{
  LWIP_UNUSED_ARG(hostname);
  LWIP_UNUSED_ARG(arg);

  if (ipaddr != NULL) {
    /* Address resolved, send request */
    LWIP_DEBUGF(SNTP_DEBUG_STATE, ("sntp_dns_found: Server address resolved, sending request\n"));
    sntp_send_request(ipaddr);
  } else {
    /* DNS resolving failed -> try another server */
    LWIP_DEBUGF(SNTP_DEBUG_WARN_STATE, ("sntp_dns_found: Failed to resolve server address resolved, trying next server\n"));
    sntp_try_next_server(NULL);
  }
}
#endif /* SNTP_SERVER_DNS */

/**
 * Send out an sntp request.
 *
 * @param arg is unused (only necessary to conform to sys_timeout)
 */
static void ICACHE_FLASH_ATTR
sntp_request(void *arg)
{
  ip_addr_t sntp_server_address;
  err_t err;

  LWIP_UNUSED_ARG(arg);

  /* initialize SNTP server address */
#if SNTP_SERVER_DNS

  if (sntp_servers[sntp_current_server].name) {
    /* always resolve the name and rely on dns-internal caching & timeout */
    ip_addr_set_any(&sntp_servers[sntp_current_server].addr);
    err = dns_gethostbyname(sntp_servers[sntp_current_server].name, &sntp_server_address,
      sntp_dns_found, NULL);
    if (err == ERR_INPROGRESS) {
      /* DNS request sent, wait for sntp_dns_found being called */
      LWIP_DEBUGF(SNTP_DEBUG_STATE, ("sntp_request: Waiting for server address to be resolved.\n"));
      return;
    } else if (err == ERR_OK) {
      sntp_servers[sntp_current_server].addr = sntp_server_address;
    }
  } else
#endif /* SNTP_SERVER_DNS */
  {
    sntp_server_address = sntp_servers[sntp_current_server].addr;
//    os_printf("sntp_server_address ip %d\n",sntp_server_address.addr);
    err = (ip_addr_isany(&sntp_server_address)) ? ERR_ARG : ERR_OK;
  }

  if (err == ERR_OK) {
    LWIP_DEBUGF(SNTP_DEBUG_TRACE, ("sntp_request: current server address is %u.%u.%u.%u\n",
      ip4_addr1(&sntp_server_address), ip4_addr2(&sntp_server_address), ip4_addr3(&sntp_server_address), ip4_addr4(&sntp_server_address)));
    sntp_send_request(&sntp_server_address);
  } else {
    /* address conversion failed, try another server */
    LWIP_DEBUGF(SNTP_DEBUG_WARN_STATE, ("sntp_request: Invalid server address, trying next server.\n"));
    sys_timeout((u32_t)SNTP_RETRY_TIMEOUT, sntp_try_next_server, NULL);
  }
}

/**
 * Initialize this module.
 * Send out request instantly or after SNTP_STARTUP_DELAY(_FUNC).
 */
void ICACHE_FLASH_ATTR
sntp_init(void)
{
#ifdef SNTP_SERVER_ADDRESS
#if SNTP_SERVER_DNS
  sntp_setservername(0, SNTP_SERVER_ADDRESS);
#else
#error SNTP_SERVER_ADDRESS string not supported SNTP_SERVER_DNS==0
#endif
#endif /* SNTP_SERVER_ADDRESS */

  if (sntp_pcb == NULL) {
    SNTP_RESET_RETRY_TIMEOUT();
    sntp_pcb = udp_new();
    LWIP_ASSERT("Failed to allocate udp pcb for sntp client", sntp_pcb != NULL);
    if (sntp_pcb != NULL) {
      udp_recv(sntp_pcb, sntp_recv, NULL);
#if SNTP_STARTUP_DELAY
      sys_timeout((u32_t)SNTP_STARTUP_DELAY_FUNC, sntp_request, NULL);
#else
      sntp_request(NULL);
#endif
    }
  }
}

/**
 * Stop this module.
 */
void ICACHE_FLASH_ATTR
sntp_stop(void)
{
  if (sntp_pcb != NULL) {
    sys_untimeout(sntp_request, NULL);
    udp_remove(sntp_pcb);
    sntp_pcb = NULL;
  }
  os_timer_disarm(&sntp_timer);
  realtime_stamp = 0;
}

#if SNTP_GET_SERVERS_FROM_DHCP
/**
 * Config SNTP server handling by IP address, name, or DHCP; clear table
 * @param set_servers_from_dhcp enable or disable getting server addresses from dhcp
 */
void
sntp_servermode_dhcp(int set_servers_from_dhcp)
{
  u8_t new_mode = set_servers_from_dhcp ? 1 : 0;
  if (sntp_set_servers_from_dhcp != new_mode) {
    sntp_set_servers_from_dhcp = new_mode;
  }
}
#endif /* SNTP_GET_SERVERS_FROM_DHCP */

/**
 * Initialize one of the NTP servers by IP address
 *
 * @param numdns the index of the NTP server to set must be < SNTP_MAX_SERVERS
 * @param dnsserver IP address of the NTP server to set
 */
void ICACHE_FLASH_ATTR
sntp_setserver(u8_t idx, ip_addr_t *server)
{
  if (idx < SNTP_MAX_SERVERS) {
    if (server != NULL) {
      sntp_servers[idx].addr = (*server);
//      os_printf("server ip %d\n",server->addr);
    } else {
      ip_addr_set_any(&sntp_servers[idx].addr);
    }
#if SNTP_SERVER_DNS
    sntp_servers[idx].name = NULL;
#endif
  }
}

#if LWIP_DHCP && SNTP_GET_SERVERS_FROM_DHCP
/**
 * Initialize one of the NTP servers by IP address, required by DHCP
 *
 * @param numdns the index of the NTP server to set must be < SNTP_MAX_SERVERS
 * @param dnsserver IP address of the NTP server to set
 */
void
dhcp_set_ntp_servers(u8_t num, ip_addr_t *server)
{
  LWIP_DEBUGF(SNTP_DEBUG_TRACE, ("sntp: %s %u.%u.%u.%u as NTP server #%u via DHCP\n",
    (sntp_set_servers_from_dhcp ? "Got" : "Rejected"),
    ip4_addr1(server), ip4_addr2(server), ip4_addr3(server), ip4_addr4(server), num));
  if (sntp_set_servers_from_dhcp && num) {
    u8_t i;
    for (i = 0; (i < num) && (i < SNTP_MAX_SERVERS); i++) {
      sntp_setserver(i, &server[i]);
    }
    for (i = num; i < SNTP_MAX_SERVERS; i++) {
      sntp_setserver(i, NULL);
    }
  }
}
#endif /* LWIP_DHCP && SNTP_GET_SERVERS_FROM_DHCP */

/**
 * Obtain one of the currently configured by IP address (or DHCP) NTP servers 
 *
 * @param numdns the index of the NTP server
 * @return IP address of the indexed NTP server or "ip_addr_any" if the NTP
 *         server has not been configured by address (or at all).
 */
ip_addr_t ICACHE_FLASH_ATTR
sntp_getserver(u8_t idx)
{
  if (idx < SNTP_MAX_SERVERS) {
    return sntp_servers[idx].addr;
  }
  return *IP_ADDR_ANY;
}

#if SNTP_SERVER_DNS
/**
 * Initialize one of the NTP servers by name
 *
 * @param numdns the index of the NTP server to set must be < SNTP_MAX_SERVERS
 * @param dnsserver DNS name of the NTP server to set, to be resolved at contact time
 */
void ICACHE_FLASH_ATTR
sntp_setservername(u8_t idx, char *server)
{
  if (idx < SNTP_MAX_SERVERS) {
    sntp_servers[idx].name = server;
  }
}

/**
 * Obtain one of the currently configured by name NTP servers.
 *
 * @param numdns the index of the NTP server
 * @return IP address of the indexed NTP server or NULL if the NTP
 *         server has not been configured by name (or at all)
 */
char * ICACHE_FLASH_ATTR
sntp_getservername(u8_t idx)
{
  if (idx < SNTP_MAX_SERVERS) {
    return sntp_servers[idx].name;
  }
  return NULL;
}
#endif /* SNTP_SERVER_DNS */

#endif /* LWIP_UDP */